KR20220131542A - Polycrystalline cubic boron nitride material - Google Patents

Abstract

The present invention relates to polycrystalline cubic boron nitride (PCBN) materials comprising a binder matrix material containing a nitride compound. The nitride compound is selected from HfN, VN and/or NbN.

Description

Polycrystalline cubic boron nitride material

The present invention relates to the field of sintered polycrystalline cubic boron nitride materials and methods of making such materials. In particular, the present invention relates to the machining of superalloys of the Inconel™ class using sintered polycrystalline cubic boron nitride material.

Polycrystalline superhard materials such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) are used for cutting, machining, It can be used in a wide variety of tools for drilling or degrading.

Abrasive compacts are widely used for cutting, turning, milling, grinding, drilling or other abrasive operations. It generally comprises ultra-hard abrasive particles dispersed in a second phase matrix. The matrix may be metal or ceramic or cermet. The ultra-hard abrasive particles may be diamond, cubic boron nitride (cBN), silicon carbide or silicon nitride, or the like. These particles can bond with each other during the commonly used high pressure and high temperature compact manufacturing processes to form a polycrystalline mass, or bond through a matrix of second phase material(s) to form a sintered polycrystalline body. have. These bodies are commonly known as polycrystalline diamond or polycrystalline cubic boron nitride and contain diamond or cBN respectively as an ultra-hard abrasive.

U.S. Patent No. 4,334,928 discloses 20 to 80% by volume of cubic boron nitride; and the remainder being a matrix of one or more matrix compound materials selected from the group consisting of carbides, nitrides, carbonitrides, borides and silicides of transition metals IVa or Va of the periodic table, mixtures thereof and solid solution compounds thereof. A sintered compact for use is taught. The methods outlined in this patent all involve joining the desired materials using mechanical milling/mixing techniques such as ball milling, mortar, and the like.

The sintered polycrystalline body can be 'backed' by forming it on a substrate. Cemented tungsten carbide, which may be used to form a suitable substrate, is formed from, for example, carbide particles dispersed in a cobalt matrix by mixing tungsten carbide particles/grains and cobalt together and then heating to solidify. To form a cutting element with a layer of superhard material such as PCD or PCBN, diamond grains or grains or CBN grains are placed adjacent to a cemented tungsten carbide body of a refractory metal enclosure such as a niobium enclosure and subjected to high pressure and pressure. High temperature treatment causes intergranular bonding between diamond grains or CBN grains to form a polycrystalline superhard diamond or polycrystalline CBN layer.

In some cases, the substrate may be fully sintered prior to attachment to the superhard material layer, while in other cases the substrate may be green (not fully sintered). In the latter case, the substrate can be completely sintered during the HPHT sintering process. The substrate may be in powder form and may be solidified during the sintering process used to sinter the superhard material layer.

Alternatively, the solid sintered polycrystalline body may be unsupported and formed free-standing without a substrate.

1 shows an exemplary method of manufacturing a sintered PCBN material. The following numbers correspond to the numbers in FIG. 1 .

S1. The matrix precursor powder is pre-mixed. Examples of matrix precursor powders include carbides and/or nitrides of titanium and aluminum. Typical average grain sizes of matrix precursor powders are between 1 μm and 10 μm.

S2. The matrix precursor powder is heat treated above 1000° C. for at least 1 hour to initiate a pre-reaction between the matrix precursor particles to form a “cake”.

S3. The cake is ground and sieved to obtain the desired particle size fraction.

S4. Cubic boron nitride (cBN) particles having an average grain size of 0.5 μm to 15 μm are added to the sieved matrix precursor powder.

S5. The resulting mixed powder is ball milled to break down the matrix precursor powder to a desired size (typically 50 nm to 700 nm), and the matrix precursor powder is intimately mixed with the cBN particles. This process can be time consuming and involves the use of milling media such as tungsten carbide balls.

S6. The resulting milled powder is dried under vacuum or low pressure above 60° C. to remove the solvent and then conditioned by slowly allowing oxygen to the system to passivate metal surfaces such as aluminum.

S7. The dry powder is sieved and a pre-composite assembly is prepared.

S8. The pre-composite assembly is heat treated above 700° C. to remove any adsorbed water or gas.

S9. The outgassed pre-composite assembly is assembled into capsules suitable for sintering.

S10. The capsule is sintered in a high pressure high temperature (HPHT) process above 1250° C. and above 4 GPa to form a sintered PCBN material.

Both tungsten (W) and cobalt (Co) are classified as important raw materials (CRM) in Europe. CRM is a raw material that is considered economically and strategically important to the European economy. In principle, they have a high risk associated with supply and are of considerable importance for key sectors of the European economy, such as consumer electronics, environmental technology, automotive, aerospace, defense, health and steel, and (available) substitutes. This is lacking. Tungsten and cobalt are the main constituents for two important classes of hard materials: cemented carbide/WC-Co and PCD/diamond-Co.

It is an object of the present invention to develop a usable alternative material for tooling operations that performs well under extreme conditions and does not require the use of a WC-Co backing.

According to a first aspect of the present invention,

40 to 95% by volume cubic boron nitride (cBN) particles; and

A binder matrix material in which the cBN particles are dispersed

There is provided a polycrystalline cubic boron nitride (PCBN) material comprising:

The content of the binder matrix material is 5% to 60% by volume of the PCBN material,

the binder matrix material comprises aluminum or a compound thereof and/or titanium or a compound thereof,

The binder matrix material further comprises an oxide compound, a nitride compound and/or an oxynitride,

The nitride compound is at least one of HfN, VN, and/or NbN.

Optionally, the oxynitride compound is present in an amount from 5% to 35% by volume of the PCBN material.

Optionally, the oxynitride compound is present in an amount from 10% to 25% by volume of the PCBN material.

Optionally, the oxynitride compound comprises AlON.

Optionally, the oxide compound comprises Al ₂ O ₃ . The Al ₂ O ₃ may be present in an amount of 10% by volume or 25% by volume of the PCBN material.

Optionally, the HfN is present in an amount of 10% or 25% by volume of the PCBN material. The binder matrix material may further comprise HfB ₂ and/or BN.

Optionally, the VN is present in an amount of 10% or 25% by volume of the PCBN material. The binder matrix material may further comprise AlN and/or BN.

Optionally, the NbN is present in an amount of 10% or 25% by volume of the PCBN material.

Optionally, said aluminum (Al) or a compound thereof is present in an amount of 2% to 15% by volume, preferably 5% to 15% by volume, more preferably 5% by volume of the PCBN material.

The PCBN material may include 50 to 70% by volume cubic boron nitride (cBN). Optionally, the PCBN material comprises 60% by volume cubic boron nitride (cBN).

According to a second aspect of the present invention,

o cubic boron nitride (cBN) powder,

o oxide-containing powders,

o a nitride-containing powder selected from HfN, VN, and/or NbN, and

o Aluminum-containing powders and/or titanium-containing powders

milling the precursor powders of

forming a green body by compacting the milled precursor powder; and

Sintering the green body at a temperature of 1250° C. to 2200° C. at a pressure of 4.0 GPa to 8.5 GPa to form a sintered polycrystalline cubic boron nitride (PCBN) material according to the first aspect of the present invention

There is provided a method of manufacturing a PCBN material comprising a.

Optionally, the oxide-containing powder comprises Al ₂ O ₃ .

Optionally, the temperature is between 1250°C and 1450°C.

Optionally, the temperature is 1350°C.

Optionally, the pressure is about 6.5 GPa.

Optionally, the temperature is between 1800°C and 2100°C.

Optionally, the pressure is about 8 GPa.

According to a third aspect of the invention, there is provided the use of the PCBN material according to the first aspect of the invention for machining a heat-resistant superalloy. Such heat-resistant superalloys may include Inconel™, an austenitic nickel-chromium based superalloy series.

BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting embodiments will now be described with reference to the accompanying drawings by way of example.
1 is a flow diagram illustrating a known exemplary method of making a sintered PCBN material.
2 is a flow chart showing an embodiment of a process used to make a PcBN material according to the present invention.
3 is an X-ray powder diffraction (XRD) pattern of sintered Example 1 produced using powder 1 containing HfN and Al ₂ O ₃ sintered at 6.5 GPa.
4 shows a scanning electron microscope (SEM) micrograph of Example 1 at a magnification of X2000.
5 is an energy dispersive X-ray spectroscopy (EDS) image of Example 1. FIG.
6 is an XRD pattern of sintered Example 2 produced using powder 2 containing VN and Al ₂ O ₃ , sintered at 6.5 GPa conditions.
7 is an SEM micrograph of Example 2 at X2000 magnification.
8 is an EDS image of Example 2.
9 is an XRD pattern of sintered Example 3 prepared using powder 2 containing VN at 8.4 GPa conditions.
10 is an image of an exemplary indentation in a PCBN material showing measurements used to calculate hardness.
11 is a line chart showing the performance of profiling aged Inconel™ 718 (HRC 44-46) of HPHT sintered samples using different binder chemistries.
12 is a bar chart showing the performance of longitudinal machining of aged Inconel™ 718 (HRC 44-46) of HPHT and LPLT sintered samples using VN and Al ₂ O ₃ binder chemistries.
FIG. 13 is an optical image showing the wear scar of a reference PCBN material using the TiC binder of FIG. 12 .
14 is an optical image showing a wear scar of a PCBN material using Al ₂ O ₃ -VN binder sintered in the HPHT condition of FIG. 12 .
15 is an optical image showing a wear scar of a PCBN material using Al ₂ O ₃ -VN binder sintered in the LPLT condition of FIG. 12 .

FIG. 2 is a flowchart illustrating exemplary steps, wherein the following numbers correspond to those in FIG. 2 .

S1. The precursor powders are milled together to form an intimate mixture and obtain the desired particle size. Precursor powders include oxide-containing powders, nitride-containing powders, aluminum powders and cBN powders. Precursor powder mixing was performed in organic solvents using a ball-milling technique and drying with a rotary evaporator.

S2. The milled precursor powders are dry pressed together to form a green body in a metal encapsulation prior to being placed in HPHT capsules. In the case of HPHT sintering, specifically, after drying, the powder is filled into a soft mold, and then compressed using a Cold Isostatic Press to compact the powder, and a high green density to reduce dimensional change after sintering. to form a green body with

The green body is then cut to different heights to fit into the HPHT capsule.

S3. The dry compressed green body is then subjected to high temperature vacuum heat treatment, followed by sintering in capsules.

The material thus prepared was sintered under the following two conditions:

- a pressure of about 6.5 GPa and a temperature of 1250°C to 1450°C, typically 1350°C; and

- a pressure of about 8 GPa and a temperature of 1800 °C to 2100 °C.

The sintering temperature was calibrated up to 1800°C using an S-type thermocouple.

S4. After sintering, the resulting sintered article was cooled to room temperature. The cooling rate is not controlled.

Example

Table 1 lists all PcBN compositions included in this work along with TiC and TiCN reference samples. In this section, LPLT stands for low pressure low temperature and HPHT stands for high pressure high temperature.

powder 1
Al ₂ O ₃ -HfN binder
Sintering conditions cBN (vol.%) Al ₂ O ₃ (vol%) HfN (vol.%) Al (vol.%) LPHT (Example 1) 60 10 25 5 powder 2
Al ₂ O ₃ -VN binder
Sintering conditions cBN (vol.%) Al ₂ O ₃ (vol%) VN (vol.%) Al (vol.%) LPLT (Example 2) & HPHT (Example 3) 60 25 10 5 powder 3
Al ₂ O ₃ -NbN binder
Sintering conditions cBN (vol.%) Al ₂ O ₃ (vol%) NbN (vol.%) Al (vol.%) HPHT 60 25 10 5 Reference 1
TiC binder
Sintering conditions cBN (vol.%) TiC (vol.%) Al (vol.%) HPHT 60 35 5 Reference 2
TiCN binder
Sintering conditions cBN (vol.%) TiCN (vol.%) Al (vol.%) HPHT 60 35 5

Examples 1, 2 and 3 are described in more detail below. Other samples provided in Table 1 (invention and reference) were prepared, characterized and subsequently tested in a similar manner to Examples 1, 2 and 3.

Example 1

S1. A precursor powder comprising Al ₂ O ₃ and HfN was mixed with cBN powder in the proportions given in Table 1 according to the detailed description of the invention.

S2. Then, the precursor powder was compressed to form a green body inside the metal capsule.

S3. The green body was placed inside the capsule and then sintered.

S4. The sintered article, the PCBN material, was cooled to room temperature for subsequent characterization and application testing.

An XRD trace is provided in FIG. 3 showing the presence of HfN, HfB ₂ , Al ₂ O ₃ and BN in the sintered article. Figure 4 shows the resulting microstructure, and the EDS image of Figure 5 provides an analysis of the microstructure composition in selected regions of the sample.

Example 2

S1. A precursor powder comprising Al ₂ O ₃ and VN was mixed with cBN powder in the proportions given in Table 1 according to the detailed description of the invention.

S2. Then, the precursor powder was compressed to form a green body inside the metal capsule.

S3. The green body was placed inside the capsule and then LPLT sintered.

S4. The sintered article, the PCBN material, was cooled to room temperature for subsequent characterization and application testing.

An XRD trace is provided in FIG. 6 showing the presence of VN, AlN, Al ₂ O ₃ and BN in the sintered article. Figure 7 shows the resulting microstructure, and the EDS image of Figure 8 provides an analysis of the microstructure composition in selected regions of the sample.

Example 3

S1. A precursor powder comprising Al ₂ O ₃ and VN was mixed with cBN powder in the proportions given in Table 1 according to the detailed description of the invention.

S2. Thereafter, the precursor powder was compressed to form a green body.

S3. The green body was cut to a predetermined size, put in a capsule, and then sintered with HPHT.

S4. The sintered article, the PCBN material, was cooled to room temperature for subsequent characterization and application testing.

An XRD trace is provided in FIG. 9 showing the presence of VN, AlN, Al ₂ O ₃ and BN in the sintered article. SEM micrographs and EDS images of the samples were taken but not included herein.

Hardness

Samples were further characterized using the Vickers hardness test. Vickers hardness (HV) is calculated by measuring the diagonal length of the indentation of the sample material (see eg FIG. 10 ) left by introducing a diamond pyramid indenter with a given load.

Table 2 shows the hardness of samples sintered from Powder 1 and Powder 2 under different conditions.

HPHT status LPLT conditions Powder 1 (Al2O3-HfN binder) n/a 35.44 GPa Powder 2 (Al2O3-VN binder) 34.33 GPa 32.08 GPa

The results show that although all samples have relatively high hardness, sintering at higher pressure and temperature only increases the hardness slightly.

application test

PCBN variants using different binder chemistries were then tested by profiling of aged Inconel™ 718 with a Rockwell hardness of HRC 44-66. The results are shown in FIG. 11 . 11 is a graph plotting the surface cut rate (v _c , m/min) with the wear rate (μm/min). Abrasion rates were measured at three different surface cut rates for most samples. These surface cut speeds were 280 m/min, 350 m/min and 420 m/min.

A reference TiC binder is generally designated 10, and a TiCN binder is designated 12. Al ₂ O ₃ -VN (HPHT) is indicated by reference 14. Al ₂ O ₃ -VN(LPLT) is indicated by reference 16. Al ₂ O ₃ -NbN (HPHT) is indicated by reference 18. Al ₂ O ₃ -HfN(HPHT) is indicated by reference 20 and contains a single data point.

11 , it can be seen that all samples in Table 1 performed better than the reference sample.

Also, referring to the samples with References 14 and 16 (i.e. with binder chemistry Al ₂ O ₃ -VN) in the graph, there is a slight difference in the wear rates when sintering in LPLT conditions compared to sintering in HPHT conditions. marginal difference).

Al ₂ O ₃ -VN (HPHT or LPLT) performed better than any sample. Al ₂ O ₃ -NbN had the second best performance, followed by Al ₂ O ₃ -HfN.

Turning now to FIG. 12 , a second application test similar to the first application was performed. The second trial focused on the performance of the Al ₂ O ₃ -VN binder chemistry in the longitudinal machining of aged Inconel™ 718 with a Rockwell hardness of HRC 44-46. Both LPLT and HPHT variants were considered.

12 is a bar chart plotting the surface cut rate v _c (m/min) with the wear rate (μm/min). A single surface cut speed of 350 m/min was used. The results showed that both the LPLT and HPHT variants performed much better than the reference TiC binder chemistry. In addition, there was minimal difference in wear rate performance between the LPLT and HPHT variants.

13-15 show the resulting abrasive scars. The wear scars of the LPLT and HPHT Al ₂ O ₃ -VN binder chemistries are significantly smaller than the TiC reference samples.

In summary, we have successfully identified several materials that are suitable for use in extreme tooling applications and are viable replacements for CRM. In particular, PCBN materials are particularly suitable for machining Inconel™ 718 and offer many advantages over cemented carbide solutions.

Justice

As used herein, "PCBN" material refers to a type of superhard material comprising grains of cBN dispersed in a matrix comprising a metal or ceramic. PCBN is an example of an ultra-hard material.

As used herein, "binder matrix material" is understood to mean a matrix material that fully or partially fills pores, interstices or interstitial regions within a polycrystalline structure.

The term "binder matrix precursor powder" is used to refer to a powder that becomes a matrix material when subjected to an HPHT or LPLT sintering process.

While the present invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims (22)

40 to 95% by volume cubic boron nitride (cBN) particles; and
A binder matrix material in which the cBN particles are dispersed
A polycrystalline cubic boron nitride (PCBN) material comprising:
The content of the binder matrix material is 5% to 60% by volume of the PCBN material,
the binder matrix material comprises aluminum or a compound thereof and/or titanium or a compound thereof,
The binder matrix material further comprises an oxide compound, a nitride compound and/or an oxynitride,
wherein the nitride compound is selected from HfN, VN, and NbN. According to claim 1,
wherein the oxynitride compound is present in an amount of 5% to 35% by volume of the PCBN material. 3. The method of claim 2,
wherein the oxynitride compound is present in an amount of 10% to 25% by volume of the PCBN material. 4. The method of claim 1, 2 or 3,
wherein the oxynitride compound comprises AlON. 5. The method according to any one of claims 1 to 4,
The PCBN material, wherein the oxide compound comprises Al ₂ O ₃ . 6. The method of claim 5,
wherein the Al ₂ O ₃ is present in an amount of 10% by volume or 25% by volume of the PCBN material. 7. The method according to any one of claims 1 to 6,
wherein the HfN is present in an amount of 10% by volume or 25% by volume of the PCBN material. 8. The method of claim 7,
wherein the binder matrix material further comprises HfB ₂ and/or BN. 9. The method according to any one of claims 1 to 8,
wherein the VN is present in an amount of 10% by volume or 25% by volume of the PCBN material. 10. The method of claim 9,
wherein the binder matrix material further comprises AlN and/or BN. 11. The method according to any one of claims 1 to 10,
wherein the NbN is present in an amount of 10% by volume or 25% by volume of the PCBN material. 12. The method according to any one of claims 1 to 11,
A PCBN material, wherein said aluminum (Al) or compound thereof is present in an amount of 2% to 15% by volume, preferably 5% to 15% by volume, more preferably 5% by volume of the PCBN material. 13. The method according to any one of claims 1 to 12,
A PCBN material comprising 50 to 70 volume percent cubic boron nitride (cBN). 14. The method according to any one of claims 1 to 13,
A PCBN material comprising 60% by volume cubic boron nitride (cBN). o cubic boron nitride (cBN) powder,
o oxide-containing powders,
o a nitride-containing powder selected from HfN, VN, and/or NbN, and
o Aluminum-containing powders and/or titanium-containing powders
milling the precursor powders of
forming a green body by compacting the milled precursor powder; and
Sintering the green body at a temperature of 1250° C. to 2200° C. at a pressure of 4.0 GPa to 8.5 GPa to form a sintered polycrystalline cubic boron nitride (PCBN) material according to any one of claims 1 to 14;
A method of manufacturing a PCBN material comprising a. 16. The method of claim 15,
wherein the oxide-containing powder comprises Al ₂ O ₃ . 17. The method of claim 15 or 16,
wherein the temperature is 1250°C to 1450°C. 18. The method of claim 17,
wherein the temperature is 1350 °C. 19. The method of claim 17 or 18,
wherein the pressure is about 6.5 GPa. 17. The method of claim 15 or 16,
The temperature is 1800 °C to 2100 °C, the manufacturing method. 21. The method of claim 20,
wherein the pressure is about 8 GPa. Use of a PCBN material according to any one of claims 1 to 14 for machining heat-resistant superalloys (HRSA).

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